One Radiator slightly warm at the top and cold at the bottom

[Tuneap]

I have one radiator which gets slightly warm at the top and is stone cold at the bottom.
I have removed the radiator, taken it outside and used the hose pipe to force water throught it while I hit it with a rubber mallet, but it didnt seem to dislodge anything. When I emptied the radiator there was a floating black particles for the first second, but while cleaning it in the garden with the hose and mallet the water is clear.

The inlet pipe is red hot so hot water is goes in but almost immedately the radiator is cold straight after that.

I did notice the radiator thermostatic valve is on the outlet but does have a bi-directional valve on.

Is there anything else I can try and do? All the other radiators are perfectly fine. Does it sound like an issue with the radiator, a build blocking it?

I have looked into getting a power flush however and been given prices around the £500 mark. I haven't got £500 spare at the moment so I was thinking of just changing the radiator for the same size one. They cost about £100 and I should be able to do it myself.

Any suggestions or advice?

Thanks

 

[stem]

Sometimes the TRV operating pin can stick removing the TRV head and giving the pin a gentle tug with pliers can free it.

Have you tried opening the lockshield valve on the inlet a bit more.

 

[Tuneap]

Sometimes the TRV operating pin can stick removing the TRV head and giving the pin a gentle tug with pliers can free it.

Have you tried opening the lockshield valve on the inlet a bit more.

Hi, yes I have tried this but doesn't seem to make any difference, I replaced the TRV valve in as a cheap possible fix but still the same. I have done done some searching and the main culprit does seem to be sludge.

I have only just finished putting the radiator back on after another attempt at cleaning it out and it does seem better. There is a definate arc of heat along the sides and top of the radiator with the vast majority of the bottom and middle very cold. It really does point to dirt buildup. It just dont think it wants to dislodge.

 

[terryplumb]

Turn every other radiator off by its TRV ( don't touch their lockshield) run heating and see if problem rad heats fully.

 

[Tuneap]

Turn every other radiator off by its TRV ( don't touch their lockshield) run heating and see if problem rad heats fully.

I have already tried that and it made no difference. Still stone cold at the bottom and in the middle.

 

[terryplumb]

If you remove radiator,take outside, and using a rubber mallet tap the rad whilst flushing it. Whilst rad is off ,open each radiator valve and let water flow out for a minute or two ,just to prove there is good flow.
If this doesn't work ,try adding x400 to the system ,let system run for a week ,if you have a magnetic filter check what it is collecting during the period.
As you do have some circulation through the problem rad ,the x400 may just breakdown anything built up in the rad.